The margin of sheet material, such as cloth, is often folded back and sewn to form a hem. The material may be manually folded back by a workers operating a sewing machine stitching the hem. However, in a commercially environment the manual folding and aligning of material is time consuming and inexact, often resulting in uneven hems or hems of different widths.
Formers have been provided which enable an operator to fold back the margin through the movement of the material through the former. Typically, these formers have plates which form a channel which progressively inverts the margin as the material is moved through the channel towards the sewing machine. However, to obtain a uniform hem these formers still rely on the operator's skill and close attention in directing the cloth through the former and in maintaining proper alignment of the material throughout sewing.
Formers have also been provided which use jets of air to urge material into a duct of the former. The duct has a guide at one end which the edge of the material abuts to maintain its alignment. This type of former is shown in U.S. Pat. No. 3,595,187. However, oftentimes the air from these jets causes the margin of the material to flutter, thus causing the margin to become misaligned.
As shown in FIG. 14, formers have also been designed to form blind hems wherein the material is folded twice, once inwardly and once outwardly and sewn along the edge of the material and the inward fold. The outward fold is unfolded to produce the finished hem shown in FIG. 13. Typically, these types of formers have a J-shaped plate which turns the material inwardly about the end of the J-shaped plate and turns the material outwardly within the J-shaped plate. The folded material is then sewn. However, these types of formers require knives to trim the edge of the material extending beyond the stitching. Thus, material is wasted and time is spent having to trim the material. Additionally, this type of hem former requires extensive training to successfully and efficiently operate the former.
Hem folders for forming blind hems have also been made which turn the material once and are used in conjunction with a sewing machine using a curved needle to stitch the edge of the material to the margin of the material. However, the curving action of the curved needle limits the speed at which the sewing machine can form the stitches and thus is very inefficient.
It thus is seen that a need remains for a former for folding back the margin of a sheet of material to form a blind hem in a more efficient and effective manner. It is to the provision of such that the present invention is primarily directed.